user
Read these two statements and explain why they contradict each other.

A piece of paper is heavier than a rock.
A rock is lighter than a piece of paper.


assistant
The two statements contradict each other because they are describing the same object in two different ways--a piece of paper is heavier than a rock, but a rock is lighter than a piece of paper. This is impossible since it is impossible for an object to be both heavier and lighter than the same object.